The gases created by the treatment of a nonferrous metal in a metallurgical furnace are usually decontaminated simply by scrubbing them in a conventional scrubbing tower. The scrubbing liquid in this tower picks up the impurities in the gases and forms a liquor that is clarified into a decantate and a sediment or sludge. The sediment of sludge is disposed of and the decantate is recirculated as the scrubbing liquid.
Particular problems are present, however, in the metallurgical treatment of nonferrous metals. In particular the gases produced by such systems frequently contain impurities which go into solution in the scrubbing liquid. As the scrubbing liquid is evaporated in the tower and supplemented with fresh water, and as the sludge is drawn away from the scrubbing liquid the the acidity thereof tends to increase considerably. Beyond a certain acidity the scrubbing liquid becomes very dangerous and must be disposed of. This is a particular problem where free chlorine gas, as a result of using potassium chloride, sodium chloride and the like in the metallurgical furnace, is present in the gas.
Not only is it difficult to handle the scrubbing liquid and is its efficiency as a scrubbing liquid greatly reduced, but even if neutralized by addition thereto of calcium carbonate or sodium hydroxide one is left with a liquid that is still a pollutant that cannot be disposed of readily.